The images above compare "subsidence," or how much the ground sank, between July 2007 and December 2010, at left, and May 2014 and January 2015, on the right. Reds and yellows indicate greater subsidence.

While the maps show that California sank more between 2007 and 2010, they also show that the rate of subsidence much greater during the more recent period.

Near Corcoran, about halfway between Los Angeles and San Francisco, a section of land sank 13 inches between May 2014 and January 2015. That amounts to about 1.6 inches a month.

Another area near El Nido, about 145 miles from San Francisco, sank 10 inches over the same period. By comparison these areas sank 37 inches and 24 inches, respectively, from 2006 to 2010.

Other areas near Yolo, a community about 87 miles from San Francisco, also sank at a record rate.

NASA collected its data using radar from satellites and airplanes.

The land is sinking because people are pumping too much water out of the ground.

The report explains that beneath the ground there are large reserves of water, called aquifers. People pump the water out using wells for uses like drinking and, more significantly, farming.

As the water is pumped out, the ground compacts and the surface sinks. When the pumping stops, the aquifers "recharge" as new water drains into them.

But a problem arises when people pull out water faster than it can recharge back into the ground. In those cases, the ground becomes more compact and loses its ability to hold as much water. That leads both to a sinking surface, and less future storage potential.

Irrigation water runs along a dried-up ditch between rice fields in Richvale, California, in May 2014.

This problem has become especially acute during the drought, which is now in its fourth year. Facing extreme water shortages, the state has cut back on how much water it delivers to farmers. They have responded to the cuts, and the shortage generally, by pumping more water out of the ground, in some cases tapping into supplies that are tens of thousands of years old.

Earlier this year, experts called the situation a crisis, and the new NASA report seems to bear out that assessment.

California does have a new groundwater law meant to rein in over-pumping, but it doesn't fully go into effect until 2040.

In the meantime, the sinking ground is breaking things like roads and, ironically, water infrastructure.

NASA found sinking has occurred along Interstate 5, and the Associated Press reported that a bridge in Firebaugh, California, was so low it was nearly scraping the water beneath it.

The Russell Avenue bridge, over the Delta Mendota Canal in Firebaugh, California, as seen on July 23.

According to the Center for Investigative Reporting, fixing the bridge would cost $2.5 million, and is just one of $80 million worth of subsidence-related repairs that are needed in the El Nido region.

A report from The Groundwater Resources Association of California also points to damage at at least one dam and an array of canal systems.

The NASA findings further note subsidence along the California Aqueduct, an artery that moves water from Northern California to the more densely populated south. The report states that "the canal lining has been raised in multiple locations over the years in order to preserve flows."

The report ultimately paints a dire picture of one of the drought's less obvious consequences. And it's a problem that, according to Mark Cowin, head of the California Department of Water Resources, needs to be corrected.

"I don't think we can end overdraft or subsidence overnight," Cowin told the AP. "We do need to take action."